FTW97LA369

As the helicopter approached a mountainous landing zone at the 8,600 foot level, the pilot applied full collective control input and the helicopter entered an uncontrolled spin and descent before impacting terrain. There was no evidence of preimpact failure of the airframe, drive train, or flight controls. The pilot said he was unable to stop the right turning despite application of full left antitorque pedal. He later told a ground witness the helicopter had 'lost tail rotor' (effectiveness).

On September 30, 1997, approximately 1145 mountain daylight time, a Hughes 369HS, N9102F, was destroyed when it impacted terrain while landing near Morgan, Utah. The private pilot and three passengers were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight being conducted under Title 14 CFR Part 91. The flight originated at Logan, Utah, approximately 1115.

In his accident report, the pilot said he made a normal approach to the landing zone from the north. The landing zone was situated approximately 8,600 feet above mean sea level. When the helicopter was about 200 meters (656 feet) from touching down, it entered an uncontrolled descent. The pilot said he applied full collective that resulted in "uncontrollable R (right, rotor) pitch." The pilot reversed direction "accelerating R (right) rotation without pedal ability to control or correct." The pilot "grounded" the left skid into the mountain side and the helicopter rolled over on its left side. Asked how the accident could have been prevented the pilot wrote, "Out of ground effect hover (test) attempt."

Because the pilot used numerous abbreviations in the narrative portion of the report, witness statements were reviewed for corroboration. A ground witness and a back seat passenger said the helicopter spun (turned) to the left. The front seat passenger and the other back seat passenger agreed with the pilot and said the helicopter spun (turned) to the right. The ground witness said the pilot later told him "he ran out of left pedal." One of the rear seat passengers said the helicopter "lost tail rotor."

The Federal Aviation Administration inspector who examined the wreckage reported he could find no evidence of a preimpact failure of the airframe, drive train, or flight controls.

According to AERODYNAMICS FOR NAVAL AVIATORS (NAVAIR 00-80T-80, c. 1960, rev. January 1965, p. 321), "Directional control in a single rotor helicopter is obtained by a tail rotor (antitorque rotor) since a conventional aerodynamic surface would not be effective at low speeds or hovering. The directional control requirements of the tail rotor on a typical shaft-driven helicopter are quite demanding since it must counteract the engine torque being supplied to the main rotor as well as provide directional control. Being a rotor in every respect, the tail rotor requires some of the engine power to generate its control forces. Unfortunately, the maximum demands of the tail rotor occur at conditions when engine power is also in great demand. The most critical condition is while hovering at maximum gross weight. The tail rotor effectiveness is determined by the rotor characteristics and the distance the tail rotor is behind the c.g."